[Autoradiographic study of DNA synthesis in rats with experimental myocardial infarct]

Rats with experimental myocardial infarction were injected with 3H-thymidine; DNA-synthesizing nuclei were counted in different parts of the heart. Myocardial infarction enhanced insignificantly the DNA synthesis in the nuclei of myocytes located at the periphery of the injured zone. However the label localization in the myocyte nuclei was rarely undoubtful. There was no increase in the number of labeled myocyte nuclei when a higher dose of 3H-thymidine was used or its injection was repeated thrice. Proliferation of connective tissue cells was activated in all the parts of the heart. The number of the connective tissue DNA-synthesizing nuclei rose within 24 hours, reached its peak in 48 hours and remained at a higher level, as compared to control throughout the experimental period. On the first day the highest count of labeled stromal nuclei was found at the periphery of the infarction and on the third day -- within the injured zone. This indicated the growth of granulation tissue from the periphery to the center of the infarction focus.